Biology subjects

Pollmann, S.

Publications and source records attributed to Pollmann, S..

13 recordsLinked to original sources

bioRxiv2025

Identification of a novel link connecting indole-3-acetamide with abscisic acid biosynthesis and signaling

Plants regulate their developmental programs and their responses to environmental changes through a complex network of small signaling compounds, known as phytohormones. The role of auxins in promoting plant growth has been extensively investigated. Furthermore, previous studies have demonstrated that the accumulation of indole-3-acetamide (IAM), an auxin precursor, results in the suppression of plant growth, particularly primary root elongation. This observation led to the hypothesis that IAM or an IAM derivative exerts negative growth regulatory effects. However, the molecular mechanism by which IAM inhibits plant growth remains largely unelucidated. To gain deeper insight into the molecular mode of action of IAM, we conducted a comprehensive genome-wide association study (GWAS) using a highly diverse collection of 166 wild Arabidopsis accessions from the Iberian Peninsula. Consequently, we identified several genomic regions associated with a reduced response to IAM under controlled in vitro conditions, which included ABA3 and GA2ox2 as candidate genes. Sequence analyses, transcriptomics studies, and comparison of three-dimensional models generated for ABA3 proteins encoded by the two major natural alleles identified in the collection of wild accessions suggested that IAM-triggered inhibition of primary root elongation is closely associated with the formation of abscisic acid (ABA) in Arabidopsis thaliana seedlings. Finally, physiological characterization of mutants for those candidate genes further corroborated that IAM activates ABA signaling. Our results demonstrate that IAM is intricately linked with ABA biosynthesis and signaling, thereby elucidating a novel node in plant hormone crosstalk.

plant biology↗

bioRxiv2025

Dynamic face-related eye movement representations in the human ventral pathway

Multiple brain areas along the ventral pathway have been known to represent face images. Here, in a magnetoencephalography (MEG) experiment, we show dynamic representations of face-related eye movements in the ventral pathway in the absence of image perception. Participants followed a dot presented on a uniform background, the movement of which represented gaze tracks acquired previously during their free-viewing of face and house pictures. We found a dominant role of the ventral stream in representing face-related gaze tracks, starting from the orbitofrontal cortex (OFC) and anterior temporal lobe (ATL), and extending to the medial temporal and ventral occipitotemporal cortex. Our findings show that the ventral pathway represents the gaze tracks used to explore faces, by which top-down prediction of face category in OFC and ATL may guide, via the medial temporal cortex or directly, face perception in the ventral occipitotemporal cortex.

neuroscience↗

bioRxiv2024

The endophytic fungus Serendipita indica alters auxin distribution in Arabidopsis thaliana roots through alteration of auxin transport and conjugation to promote plant growth

Plants share their habitats with a multitude of different microbes. This close vicinity promoted the evolution of inter-organismic interactions between plants and many different microorganisms that provide mutual growth benefits both to the plant and the microbial partner. The symbiosis of Arabidopsis thaliana with the beneficial root colonizing endophyte Serendipita indica represents a well-studied system. Co-colonization of Arabidopsis roots with S. indica significantly promotes plant growth. Due to the notable phenotypic alterations of fungus-infected root systems, the involvement of a reprogramming of plant hormone levels, especially that of indole-3-acetic acid, has been suggested earlier. However, until now, the molecular mechanism by which S. indica promotes plant growth remains largely unknown. This study used comprehensive transcriptomics, metabolomics, reverse genetics, and life cell imaging to reveal the intricacies of auxin-related processes that affect root growth in the symbiosis between A. thaliana and S. indica. Our experiments revealed the essential role of tightly controlled auxin conjugation in the plant-fungus interaction. It particularly highlighted the importance of two GRETCHEN HAGEN 3 (GH3) genes, GH3.5 and GH3.17, for the fungus infection-triggered stimulation of biomass production, thus broadening our knowledge about the function of GH3s in plants. Furthermore, we provide evidence for the transcriptional alteration of the PIN2 auxin transporter gene in roots of Arabidopsis seedlings infected with S. indica and demonstrate that this transcriptional adjustment affects auxin signaling in roots, which results in increased plant growth.

plant biology↗

bioRxiv2020

Perturbations of the AMI1 IAM-amidohydrolase expression trigger plant stress responses in Arabidopsis thaliana

The evolutionary success of plants relies to a large extent on their extraordinary ability to adapt to changes in their environment. These adaptations require that plants balance their growth with their stress responses. Plant hormones are crucial mediators orchestrating the underlying adaptive processes. However, whether and how the growth-related hormone auxin and the stress-related hormones jasmonic acid (JA), salicylic acid, and abscisic acid (ABA) are coordinated remains largely elusive. Here, we analyze the physiological role of AMIDASE 1 (AMI1) in plant growth and its possible connection to plant adaptations to abiotic stresses. AMI1 contributes to cellular auxin homeostasis by catalyzing the conversion of indole-acetamide into the major plant auxin indole-3-acetic acid. Functional impairment of AMI1 increases the plants stress status rendering mutant plants more susceptible to abiotic stresses. Transcriptomic analysis of ami1 mutants disclosed the reprogramming of a considerable number of stress-related genes, including JA and ABA biosynthesis genes. The ami1 mutants exhibit only moderately repressed growth, but an enhanced ABA accumulation, which suggests a role for AMI1 in the crosstalk between auxin and ABA. Altogether, our results suggest that AMI1 is involved in coordinating the trade-off between plant growth and stress responses, balancing auxin with ABA homeostasis. HIGHLIGHTThe IAM amidohydrolase AMI1 catalyzes the conversion of IAM into IAA in vivo. Expression of AMI1 is specifically repressed by osmotic stress conditions, which triggers ABA biosynthesis through the induction of NCED3, thereby linking auxin homeostasis with plant stress responses.

plant biology↗

bioRxiv2020

Spatial accumulation of salicylic acid is in effector-triggered immunity of potato against viruses regulated by RBOHD

While activation of resistance (R) proteins has been intensively studied, the downstream signaling mechanisms leading to restriction of pathogen remain mostly unknown. We studied the immunity network response conditioned by the potato Ny-1 gene against potato virus Y. We analyzed the processes in the cell death zone and surrounding tissue on the biochemical and gene expression levels to reveal spatiotemporal regulation of immune response. We show that the transcriptional response in the cell death zone and surrounding tissue is dependent on salicylic acid (SA). For some genes, spatiotemporal regulation is completely lost in SA-deficient line, while the others show different response, indicating multiple connections between hormonal signaling modules. The induction of NADPH oxidase RBOHD expression occurs specifically on the lesion border during resistance response. In plants with silenced RBOHD, the functionality of resistance response is perturbed and virus spread is not arrested at the site of infection. RBOHD is required for spatial accumulation of SA, and conversely RBOHD is under transcriptional regulation of SA signaling. Using spatially resolved RNA-Seq, we also identified spatial regulation of an UDP-glucosyltransferase, another component in feedback activation of SA biosynthesis, thus deciphering a novel aspect of resistance signaling.

plant biology↗

bioRxiv2019

The Role of Proactive and Reactive Cognitive Control for Target Selection in Multiple-Target Search

Cognitive control can involve proactive (preparatory) and reactive (corrective) mechanisms. Using a gaze-contingent eye tracking paradigm combined with fMRI, we investigated the involvement of these different modes of control and their underlying neural networks, when switching between different targets in multiple-target search. Participants simultaneously searched for two possible targets presented among distractors, and selected one of them. In one condition, only one of the targets was available in each display, so that the choice was imposed, and reactive control would be required. In the other condition, both targets were present, giving observers free choice over target selection, and allowing for proactive control. Switch costs emerged only when targets were imposed and not when target selection was free. We found differential levels of activity in the frontoparietal control network depending on whether target switches were free or imposed. Furthermore, we observed core regions of the default mode network to be active during target repetitions, indicating reduced control on these trials. Free and imposed switches jointly activated parietal and posterior frontal cortices, while free switches additionally activated anterior frontal cortices. These findings highlight unique contributions of proactive and reactive control during visual search.

neuroscience↗

bioRxiv2018

Cross-task perceptual learning of object recognition in simulated retinal implant perception

The perception gained by retina implants (RI) is limited, which asks for a learning regime to improve patients visual perception. Here we simulated RI vision and investigated if object recognition in RI patients can be improved and maintained through training. Importantly, we asked if the trained object recognition can be generalized to a new task context, and to new viewpoints of the trained objects. For this purpose, we adopted two training tasks, a naming task where participants had to choose the correct label out of other distracting labels for the presented object, and a discrimination task where participants had to choose the correct object out of other distracting objects to match the presented label. Our results showed that, despite of the task order, recognition performance was improved in both tasks and lasted at least for a week. The improved object recognition, however, can be transferred only from the naming task to the discrimination task but not vice versa. Additionally, the trained object recognition can be transferred to new viewpoints of the trained objects only in the naming task but not in the discrimination task. Training with the naming task is therefore recommended for RI patients to achieve persistent and flexible visual perception.

neuroscience↗

bioRxiv2018

Not scene learning, but attentional processing is superior in team sport athletes and action video game players

We tested if high-level athletes or action video game players have superior context learning skills. Incidental context learning was tested in a spatial contextual cueing paradigm. We found comparable contextual cueing of visual search in repeated displays in high-level amateur handball players, dedicated action video game players and normal controls. In contrast, both handball players and action video game players showed faster search than controls, measured as search time per display item, independent of display repetition. Thus, our data do not indicate superior context learning skills in athletes or action video game players. Rather, both groups showed more efficient visual search in abstract displays that were not related to sport-specific situations.

neuroscience↗

bioRxiv2018

The effect of acquisition resolution on orientation decoding from V1: comparison of 3T and 7T

Previously published results indicate that the accuracy of decoding visual orientation from 7T fMRI data of V1 peaks at spatial acquisition resolutions that are routinely accessible with more conventional 3T scanners. This study directly compares the decoding performance between a 3T and a 7T dataset that were acquired using the same stimulation paradigm by applying an identical analysis procedure. The results indicate that decoding models built on 3T data are comparatively impaired. Moreover, we found no evidence for a strong coupling of BOLD signal change magnitude or temporal signal to noise ratio (tSNR) with decoding performance. Direct enhancement of tSNR via multiband fMRI acquisition at the same resolution did not translate into improved decoding performance. Additional voxel selection can boost 3T decoding performance to the 7T level only at a 3mm acquisition resolution. In both datasets the BOLD signal available for orientation decoding is spatially broadband, but, consistent with the size of the BOLD point-spread-function, decoding models at 3T utilize spatially coarser image components.

neuroscience↗

bioRxiv2018

Substrate channeling in oxylipin biosynthesis through a protein complex in the plastid envelope of Arabidopsis thaliana

Oxygenated membrane fatty acid derivatives dubbed oxylipins play important roles in the plants defense against biotic and abiotic cues. Plants challenged by insect pests, for example, synthesize a blend of different defense compounds that, amongst others, comprise volatile aldehydes and jasmonic acid (JA). Because all oxylipins are derived from the same pathway, we asked how their synthesis might be regulated and focused on two closely related, atypical cytochrome P450 enzymes designated CYP74A and CYP74B, i.e., allene oxide synthase (AOS) and hydroperoxide lyase (HPL). Both enzymes compete for the same substrate but give rise to different products. While the final product of the AOS branch is JA, those of the HPL branch comprise volatile aldehydes and alcohols. AOS and HPL are plastid envelope enzymes in Arabidopsis thaliana but accumulate at different locations. Biochemical experiments identified AOS as constituent of complexes also containing lipoxygenase 2 (LOX2) and allene oxide cyclase (AOC), which catalyze consecutive steps in JA precursor biosynthesis, while excluding the concurrent HPL reaction. Based on published X-ray data, the structure of this complex could be modelled and amino acids involved in catalysis and subunit interactions identified. Genetic studies identified the microRNA 319 (miR319)-regulated clade of TCP (TEOSINTE BRANCHED/CYCLOIDEA/PCF) transcription factor genes and CORONATINE INSENSITIVE 1 (COI1) to control JA production through the AOS-LOX2-AOC2 complex. Together, our results define a molecular branch point in oxylipin biosynthesis that allows fine-tuning the plants defense machinery in response to biotic and abiotic stimuli.

cell biology↗

bioRxiv2018

Spatial contextual cueing is not a limiting factor for expert performance in the domain of team sports or action video game playing

We investigated in two experiments if handball and action video game players show improved implicit learning of repeated spatial configurations for efficient search guidance in comparison to a control group without sport or video game proficiency. To this end, we used both a sport-specific pseudo 3-D contextual cueing task and the original contextual cueing paradigm (Chun & Jiang, 1998). Contextual cueing was present in all groups. However, handball and action video game players did not differ in the strength of contextual cueing from the control group. Action video game players had shorter search times than controls in both experiments. In contrast, the handball players searched faster than controls in the sport-specific displays of Experiment 1 but not in the symbolic search task of Experiment 2. Thus, our findings provide no evidence that contextual cueing is a limiting factor for expert performance in the domain of team sports or action video game playing.

neuroscience↗

bioRxiv2017

Tolerance To PVY Infection In Potato Is Conditioned By Perturbation Of Small RNA-Gibberellin Regulatory Network

Potato virus Y is the most economically important potato viral pathogen. We aimed at unraveling the roles of small RNAs (sRNAs) in the complex immune signaling network controlling the establishment of tolerant response of potato cv. Desiree to the virus. We constructed a sRNA regulatory network connecting sRNAs and their targets to link sRNA level responses to physiological processes. We discovered an interesting novel sRNAs-gibberellin regulatory circuit being activated as early as 3 days post inoculation before viral multiplication can be detected. Increased levels of miR167 and phasiRNA931 were reflected in decreased levels of transcripts involved in gibberellin biosynthesis. Moreover, decreased concentration of gibberellin confirmed this regulation. The functional relation between lower activity of gibberellin signaling and reduced disease severity was previously confirmed in Arabidopsis-virus interaction using knockout mutants. We further showed that this regulation is salicylic acid-dependent as the response of sRNA network was attenuated in salicylic acid-depleted transgenic counterpart NahG-Desiree expressing severe disease symptoms. Besides downregulation of gibberellin signaling, regulation of several other parts of sRNA network in tolerant Desiree revealed similarities to responses observed in mutualistic symbiotic interactions. The intertwining of different regulatory networks revealed shows how developmental signaling, disease symptom development and stress signaling can be balanced.

plant biology↗

bioRxiv2016

The effect of acquisition resolution on orientation decoding from V1 BOLD fMRI at 7 Tesla

A decade after it was shown that the orientation of visual grating stimuli can be decoded from human visual cortex activity by means of multivariate pattern classification of BOLD fMRI data, numerous studies have investigated which aspects of neuronal activity are reflected in BOLD response patterns and are accessible for decoding. However, it remains inconclusive what the effect of acquisition resolution on BOLD fMRI decoding analyses is. The present study is the first to provide empirical ultra high-field fMRI data recorded at four spatial resolutions (0.8 mm, 1.4 mm, 2 mm, and 3 mm isotropic voxel size) on this topic -- in order to test hypotheses on the strength and spatial scale of orientation discriminating signals. We present detailed analysis, in line with predictions from previous simulation studies, about how the performance of orientation decoding varies with different acquisition resolutions. Moreover, we also examine different spatial filtering procedures and its effects on orientation decoding. Here we show that higher-resolution scans with subsequent down-sampling or low-pass filtering yield no benefit over scans natively recorded in the corresponding lower resolution regarding decoding accuracy. The orientation-related signal in the BOLD fMRI data is spatially broadband in nature, includes both high spatial frequency components, as well as large-scale biases previously proposed in the literature. Moreover, we found above chance-level contribution from large draining veins to orientation decoding. Acquired raw data were publicly released to facilitate further investigation.

neuroscience↗